Inositol hexaphosphate increases mucin loss from the digestive tract of ducks.

The effects of different forms of inositol hexaphosphate (IP6, phytate) on mucin excretion from the digestive tract of ducks were investigated. Forty-eight ten-wk-old male ducks were grouped by weight into eight blocks of six cages with one bird per cage. On the first day of experimentation, birds received by intubation six dextrose-based diets arranged in a 2 × 3 factorial consisting of phytase (0 or 1000 units) and a form of IP6 (no IP6, free phytic acid or magnesium-potassium phytate). During the 54 h following feeding, excreta were continuously collected and frozen until analysed. The amount of mucin and amino acids, threonine, valine and tyrosine, in excreta increased in ducks fed with either magnesium-potassium phytate or free phytic acid. The increase in mucin excretion was more in birds fed with magnesium-potassium phytate than those fed with free phytic acid. The loss of arginine, isoleucine, leucine, lysine and phenylyalanine in excreta was reduced by the presence of microbial phytase. It is concluded that the form of IP6 fed to ducks affects the extent of mucin excretion and also the extent and nature of endogenous amino acid losses in the excreta. Supplementation with exogenous microbial phytase reduced some of the IP6 feeding-induced endogenous intestinal amino acid losses.

Dietary phytate (inositol hexaphosphate) regulates the activity of intestinal mucosa phytase.

The role of dietary phytate (inositol hexaphosphate) in the regulation of intestinal mucosa phytase was investigated in chicks. Seven-day-old chicks were grouped by weight into six blocks of three cages with six birds per cage. Three purified diets [a chemically defined casein diet, a chemically defined casein diet plus sodium phytate (20 g/kg diet) and a chemically defined casein diet plus sodium phytate (20 g/kg diet) and microbial phytase (1000 units/kg diet)] were randomly assigned to cages within each block. Chicks were fed experimental diets from 8 to 22 days of age then killed, and duodenal mucosa and left tibia removed. Phytase activity in duodenal mucosa, growth performance and bone ash content were determined. Addition of phytate to the chemically defined casein diet reduced (p < 0.05) the V(max) of the duodenal brush border phytase, but the K(m) of the enzyme was not affected. Addition of phytate also reduced (p < 0.05) weight gain, feed intake, feed efficiency and percentage ash. Addition of microbial phytase fully restored the feed efficiency (p < 0.05), but V(max) and body weight gain were only partially restored (p < 0.05). In conclusion, it would seem that dietary phytates non-competitively inhibit intestinal mucosa phytase.

Dietary cholecalciferol and phosphorus influence intestinal mucosa phytase activity in broiler chicks.

1. The role of cholecalciferol and phosphorus in the regulation of intestinal mucosa phytase was investigated in broiler chicks. 2. A total of 144 7-d-old male broiler chicks were grouped by weight into 6 blocks of 4 cages with 6 broiler chicks per cage. Four maize-soybean meal-based mash diets were randomly assigned to cages within each block. The 4 diets consisted of cholecalciferol at 0 or 75 microg/kg and total phosphorus at 3.6 or 7.0 g/kg in a 2 x 2 factorial arrangement. The birds were given the experimental diets for 12 d under conditions which excluded ultraviolet light. 3. Broiler chicks fed on diets with the higher concentration of cholecalciferol had higher Vmax and Km of the mucosa phytase, weight gain, feed intake, feed efficiency and percentage tibia ash, higher ileal digestibility of dry matter, energy, phosphorus (P) and calcium (Ca), and increased retention of dry matter, nitrogen, P, Ca and energy. 4. Broiler chicks receiving diets with the higher P concentration showed lower Vmax and Km of the intestinal mucosa phytase but greater weight gain, feed intake, feed efficiency and percentage tibia ash, higher ileal digestibility of dry matter, energy, P and nitrogen, and increased retention of dry matter, energy, nitrogen and Ca. 5. In conclusion, both dietary P and cholecalciferol influenced the activity of intestinal mucosa phytase.

Efficacy of an evolved Escherichia coli phytase in diets of broiler chicks.

An evolved Escherichia coli-derived phytase was evaluated for its efficacy in improving growth performance and nutrient utilization of broiler chicks. One hundred forty-four 7-d-old male broiler chicks were grouped by weight into 6 blocks of 6 cages with 4 birds per cage. Six corn-soybean meal-based mash diets were randomly assigned to cages within each block. The 6 diets were adequate P (7.7 g of P/kg of diet), low P (3.9 g of P/kg of diet), low P diet plus 0.75 or 1.5 g of inorganic P from monosodium phosphate, and low P diet plus the evolved Escherichia coli phytase at 500 or 1,000 units/kg of diet. The chicks were fed the experimental diets from 8 to 22 d of age. The evolved Escherichia coli phytase improved weight gain (P < 0.05), feed intake (P < 0.01), percentage tibia ash (P < 0.01), and retention of P (P < 0.001), Ca (P < 0.01), N (P < 0.05), and a number of amino acids (P < 0.05). The evolved Escherichia coli phytase was, therefore, efficacious in improving broiler growth performance, bone characteristics, and retention of P, Ca, N, and a number of amino acids.

Evaluation of microbial phytase in broiler diets.

Two trials were conducted to evaluate the efficacy of a new microbial phytase (Phyzyme XP) for broiler chicks. Trial 1 used 192 8-d-old male broilers in a 14-d trial to assess growth and nutrient utilization. Dietary treatments (221.9 g/kg CP) included a positive control [5.0 g/kg nonphytate P (NPP)], negative control (1.2 g/kg NPP), and negative control plus 500 or 1,000 phytase units/kg of diet. Phytase addition increased weight gain, feed intake, feed efficiency, and tibia and toe ash (linear, P < 0.01) with tibia ash also responding quadratically (P < 0.05). Apparent ileal digestibility of P (linear and quadratic, P < 0.05), tryptophan, and valine (linear, P < 0.05) also increased. Linear and quadratic responses were observed for retention of DM, nitrogen, P, and several amino acids (P < 0.05) with added phytase. Trial 2 utilized 576 1-d-old male broilers over a 42-d period to evaluate growth performance. Diets were formulated for starter (222.7 g/kg CP) and grower (201.5 g/kg CP) phases and included a positive control (starter and grower, 5.0 and 3.8 g/kg NPP, respectively); negative control (starter and grower, 2.4 and 1.8 g/kg NPP, respectively); negative control plus 500, 750, or 1,000 phytase units/kg; and negative control plus 500 phytase units/kg of Natuphos phytase. Phytase increased weight gain and feed intake (starter, grower, overall) as well as feed efficiency during the starter period (linear, P < 0.05). Feed intake was also improved during the grower period and overall (quadratic, P < 0.05). Tibia and toe ash of birds fed for the first 21 d increased (linear, P < 0.05) with tibia ash also increasing quadratically (P < 0.05). Overall, tibia and toe ash were improved due to phytase addition (linear and quadratic, P < 0.05). In conclusion, this microbial phytase, derived from Escherichia coli and expressed in Schizosaccaromyces pombe, elicited improved growth performance, bone mineralization, and P utilization in broiler chicks.

The yeast production system in which Escherichia coli phytase is expressed may affect growth performance, bone ash, and nutrient use in broiler chicks.

The efficacy of three Escherichia coli-derived phytase preparations on the performance and nutrient utilization of broiler chicks was evaluated. Two hundred sixteen 7-d-old male broiler chicks were grouped by weight into 6 blocks of 6 cages with 6 birds per cage. Six corn-soybean meal-based diets were randomly assigned to cages within each block. The 6 diets were adequate P, very low P, and low P and contained (g of P/kg of diet) 7.7, 4.0, and 5.1, respectively; and low-P diet plus phytase preparation A, B, or C at 1,000 units/kg of feed. All 3 phytase preparations were produced in different yeast production systems with slightly different glycosylation patterns. Preparation A was produced in Pichia pastoris, B in Schizosaccharomyces pombe, and C in Saccharomyces cerevisiae. The chicks were fed the experimental diets from 8 to 22 d of age. Excreta samples were collected between 17 and 21 d of age. At the end of the study, blood was collected, chicks were killed, and tibiae were removed from 3 birds per cage. Weight gain, feed intake, and feed efficiency among the 3 phytase preparations did not differ, although only phytase A diet outperformed (P < 0.05) the low-P diet in terms of weight gain and feed efficiency. All 3 phytase diets outperformed (P < 0.05) the low-P diet in bone mineral content, density, strength, percentage ash, P retention, and serum P levels. Phytase B diet outperformed the adequate-P diet in bone strength. All 3 preparations increased (P < 0.05) Ca retention with phytase B or C showing a better retention of Ca than phytase A. All 3 phytase preparations showed similar P use as indicated by BW gain and tibia bone characteristics.

Bone densitometry as an indicator of percentage tibia ash in broiler chicks fed varying dietary calcium and phosphorus levels.

The relative sensitivity of tibia bone mineral content (BMC) and density (BMD), percentage ash (ash), and shear force as indicators for dietary Ca and P was compared in 3-wk-old broiler chicks. One hundred eight 7-d-old chicks were grouped by weight into 6 blocks of 3 cages each with 6 birds per cage. Three corn-soybean meal-based diets were randomly assigned to cages within each block. The diets were low P, medium P, and adequate P and were formulated to contain 4.0, 5.1, and 7.8 g of total P/kg feed, respectively; and 5.1, 6.7, and 10.0 g of Ca/kg feed, respectively. The chicks were fed the experimental diets for 14 d. On d 22, chicks were killed, and tibiae were removed from 3 birds/cage. Weight gain, feed intake, feed efficiency, BMC, BMD, shear force, and ash were determined. The BMC and BMD were determined using dual energy x-ray absorptiometry. Correlations among the various bone status variables and dietary Ca and P were determined. Growth performance criteria and ash increased linearly, and BMC and BMD increased linearly and quadratically as dietary concentrations of Ca and P increased. The correlation coefficient between dietary Ca and BMC, BMD, shear force, or ash was 0.89, 0.91, 0.50, or 0.89, respectively; and between dietary P and BMC, BMD, shear force, or ash was 0.88, 0.91, 0.48, or 0.89, respectively. The correlation coefficient between ash and BMC, BMD, or shear force was 0.92, 0.93, or 0.67, respectively. The correlation coefficients for linear regression between shear force and BMC or BMD was 0.56. The regression model for predicting percentage ash using BMD was as follows: percentage ash = 24 + (240 x BMD) with an r2 of 86%. It is concluded that in broiler chicks, tibia ash, BMC, and BMD may be more sensitive than shear force as indicators of dietary Ca and P concentrations and that BMD as measured by dual energy x-ray absorptiometry may be used to predict percentage of tibia ash.